1. Field of the Invention
This invention relates to novel fuel compositions for use in internal combustion engines. More particularly, this invention relates to gasoline-ethanol fuel mixtures having carburetor detergency properties. The invention also is concerned with a process for conferring carburetor detergency properties to ethanol in gasoline fuel mixtures.
2. Description of the Prior
Worldwide concern over the growing shortages of crude oil supplies has promoted the use of many materials as blending agents in gasoline to extend the fuel supply. From the engine or motor vehicle manufacturers' point of view, it seems easiest to employ alcohol blended with gasoline. Methanol, ethanol and t-butyl alcohol have emerged as the most widely used alcohol blending agents. Recently, a high level of interest has been shown in the use of "Gasohol," defined herein as a blend of gasoline with from about 5 to about 30 volume percent ethanol, as an automotive fuel. Interest has been especially high in countries such as Brazil which have an intense cultivation of sugar cane, mandioca and other raw materials of vegetable origin adequate for the production of ethanol.
The use of a polar oxygenate such as ethanol in gasoline blends, however, has far reaching consequences. One of these is the formation of deposits in the fuel induction system such as the carburetor and around the intake valves. These deposits interfere with the efficient operation of the engine and can lead to lower mileage and increased exhaust emissions. It is believed that deposit formation may be caused by several factors. One of these may be the loosening of rust by the alcohol from the walls in pipelines and storage tanks which is then transported through the system until it finds its way into the fuel induction system of the engine. Another factor may be the presence of trace amounts of acetic acid, acetaldehyde, acetate and n-butanol in the ethanol-gasoline blends which are formed during the production of the alcohol during fermentation. These impurities likewise may ultimately end up in the fuel induction system of the engine and contribute to deposit formation. Other factors which may contribute to deposit formation may be phase separation problems which occur because commercial ethanol (hydrous ethanol) has limited solubility in gasoline and the presence of dissolved mineral salts, such as sodium chloride, which may find their way into the fuel during production, storage and transportation. In fact, applicant has established that heavier carburetor deposits are obtained with the use of gasohol than with gasoline as will be demonstrated below.
Thus, there is presently a need for a fuel induction detergent that will either retard or prevent the formation of deposits in the fuel induction system of an internal combustion engine operated on an ethanol-gasoline fuel mixture. Further, it is important that the detergent be effective in very small quantities to avoid any adverse effects, such as adding to the gum component of the fuel, etc., as well as to minimize cost. The detergent compositions of the present invention satisfy these needs.
It is known in the art that the inclusion in gasoline of the condensation product of a high molecular weight alkylphenol, an aldehyde and an amine having an H--N&gt; group, as well as concentrates containing in addition to the condensation product other components such as demulsifying agents, solvents, corrosion inhibitors and the like, improve intake system cleanliness. Illustrative patents include U.S. Pat. Nos. 3,649,229; 3,752,657; 3,994,698; 4,116,644; Austrian Pat. No. 315,994; British Pat. No. 1,368,532 and German Pat. No. 2,209,579.
It is generally appreciated, however, by those skilled in the art that the blending of components to make a suitable concentrate to be used in gasoline compositions is very difficult. The components must not only be used in amounts which confer the required properties on the gasoline concentrate, but the components must also be compatible with each other under use and storage conditions. Furthermore, some components used for different functions can be found to be mutually antagonistic such as mixtures of corrosion inhibitors and demulsifiers. When antagonism occurs, loss of desired function is a result.
Given the acknowledged difficulties in selecting specific components to make an effective detergency concentrate for use in gasoline, it was quite surprising to discover that a Mannich base concentrate, such as the concentrate of the present invention, would function effectively as a fuel induction detergent in engines operated on gasoline-alcohol fuel mixtures, such as gasohol defined hereinabove.